The present invention relates to an improved valve train for an internal combustion engine, and more particularly, to a valve deactivator assembly for use therein, and even more particularly, to such a valve deactivator of the type utilizing a latching pin arrangement.
Although the valve deactivator assembly of the present invention may be utilized to introduce some additional lash into the valve train, such that the valves open and close by an amount less than the normal opening and closing, the invention is especially suited for introducing into the valve train sufficient lash (also referred to hereinafter as "lost motion"), such that the valves no longer open and close at all, and the invention will be described in connection therewith.
Valve deactivators of the general type to which the invention relates are known, especially in connection with internal combustion engines having push rod type valve gear train. In such a gear train, there is a rocker arm, with one end of the rocker arm engaging a push rod, and the other end engaging the engine poppet valve. Typically, a central portion of the rocker arm is fixed relative to the cylinder head (or other suitable structure) by a fulcrum arrangement as is well known to those skilled in the art, in which the fulcrum normally prevents movement of the central portion of the rocker arm in an "up and down" direction. At the same time, the fulcrum permits the rocker arm to engage in cyclical, pivotal movement, in response to the cyclical movement of the push rod, which results in the engagement of the push rod with the lobes of a rotating cam shaft.
There are a number of known valve deactivator assemblies which are operably associated with the fulcrum portion of the rocker arm in a push rod type valve gear train. Such known valve deactivator assemblies, when in the latched condition, restrain the fulcrum portion of the rocker arm to cause the rocker arm to move in its normal cyclical, pivotal movement. However, in an unlatched condition, the valve deactivator assembly permits the fulcrum portion of the rocker arm to engage in "lost motion" such that the cyclical, pivotal movement of the push rod causes the rocker arm to undergo cyclical, pivotal movement about the end which is in engagement with the engine poppet valve. In other words, the rocker arm merely pivots, but the engine poppet valve does not move, and hence, is in its deactivated condition.
A different approach to valve deactivation in a push rod type valve gear train is illustrated and described in copending application U.S.S.N. 09/255,366, filed Feb. 23, 1999 in the name of Kynan L. Church for a "Hydraulically Actuated Valve Deactivating Roller Follower". In the copending application, the valve deactivation is accomplished in a roller follower of a type having an outer body which moves with the roller follower, and an inner body which imparts motion to the push rod. The valve deactivator has either an unlatched condition, in which lost motion occurs, or a latched condition, in which the inner and outer bodies are latched to each other and motion imparted to the roller follower by the cam is, in turn, transmitted to the push rod to provide normal valve opening and closing.
A generally similar type of valve deactivator is illustrated and described in U.S. Pat. No. 5,655,487, for use in an overhead cam ("OHC") engine, of the type utilizing an end pivot rocker arm. In a valve gear train of the type described above, the pivot point for the end of the rocker arm is a hydraulic lash adjuster ("HLA"), with the opposite end of the rocker arm being in engagement with the engine poppet valve.
In the valve deactivator of the above-cited patent, the latching arrangement between the inner and outer bodies is configured such that the inner body must be maintained in a predetermined rotational orientation within the outer body, in order for proper latching and unlatching to occur. Such a need for maintaining rotational orientation of the inner body member, relative to the outer body member, adds substantially to the overall complexity and cost of both the manufacture and assembly of the valve deactivating HLA. In connection with the development of the present invention, it has also been determined that another disadvantage of the valve deactivator of the cited patent is that, when the latching mechanism is latched, all of the gear train force being supported by the latching mechanism is being carried over a relatively small area, thus resulting in higher than desirable surface stresses in the latch mechanism.